I have a programmable Speed Hut speedometer that uses the PPM and is calculated by driving 2 miles and it learns on its own. My MPH readings are off 3 mph while datalogging vs GPS and my Speedo. I need to get that lowered down but also; I noticed my original tune used the wrong number of VSS teeth (45 instead of 40). I know they are both used but the VSS PPM is mainly for the Speedo. Can you adjust one and not the other, or do you need to apply a certain percentage of change to both?

2000 4L60E with 25.66 tires and 3.73 gears and 40 tooth VSS gear